Field of the Invention
The invention relates to a sensing method. Particularly, the invention relates to a touch sensing method of a touch panel.
Description of Related Art
Along with development of a multi-touch technique, a capacitive touch technique has become one of main streams of the touch panel techniques. Since human body is a conductor, when the human body approaches to a capacitive touch panel, a capacitance generated between a transparent electrode of the capacitive touch panel and the human body due to electrostatic binding is varied. By measuring capacitance variations of sensing lines on the capacitive touch panel, a position of a touch point is determined.
In order to detect the capacitance variations of the sensing lines, when the touch panel is manufactured, an area of the sensing lines arranged along an X-direction and a Y-direction is designed in a certain size. However, the above method may limit the number of the sensing lines, and accordingly decrease a resolution of touch coordinates.
To resolve the above problem, a technique of increasing the resolution of the touch coordinates through linear interpolation is provided. In detail, when a finger touches the touch panel, a difference between the sensing line touched by the finger and an environmental capacitance is increased to be greater than a threshold. In order to improve the accuracy of the touch coordinates, the system performs a linear interpolation operation on differences of the adjacent sensing lines to obtain exact coordinates of the touch point. However, since the number of fingers that can be resolved by the touch panel is determined by the number of the sensing lines arranged along the X-direction and the Y-direction, the number of the fingers that can be resolved by the touch panel is not increased by using the linear interpolation method. For example, when two fingers are too close to each other, the difference of the sensing line between the two fingers is also higher than the threshold, which may cause a situation that a two-point touch is mistaken as a single-point touch, and wrong touch coordinates are accordingly obtained.
On the other hand, in an ideal multi-finger touch operation, although the user generally touches the touch panel through a small-area fingertip, the user is also liable to touch the touch panel through a finger pulp to produce a large-area press. Besides, the user may often unintentionally put the palm or a thumb portion on the touch panel to cause a large-area press. In case of such large-area press, the system may misjudge one touch point as two touch points due to influences of uneven distribution of the capacitances of the touch surface and an environmental noise. Alternatively, due to influence of the noise, the measured coordinates are constantly varied along with time to cause a coordinate shift phenomenon, so that the correct touch coordinates cannot be obtained.
Therefore, the linear interpolation method used by the conventional touch panel cannot resolve the problem of coordinate misjudgement caused by inadequate distance resolution between the fingers, and coordinates of a large-area touch point cannot be correctly detected.